Ability Sequence

Starting Caitlyn

Easy to play hard to master
Caitly is due to her long range rather easy to pick up in the lane phase, however in the lategame you will bump into some difficulties i will discuss those later in the guide.

Runes

Marks:9x Greater Mark of Desolation

Why? the flat armor pen almost lets you hit the oppposing laner as if he has no armor i take these because it's getting rather common to take armor seals and masteries in the bottom lane . >?

Seals:9x Greater Seal of Resilience

Why? because it helps against the early herras

Glyphs:9x Greater Glyph of Shielding

Why, it helps quite much against lategame AP carries so you won't get oneshot

Quints:3x Greater Quintessence of Strength

Why? Helps last-hitting minions and extra AD is always nice throughout the game

Masteries

21/9/0:

Well these masteries i take for all AD carries i play
For masteries i usually run 21/9/0 i go for the 9 in Defense instead of utility purely for personal preference newcomers might favor the extra mana from the utility tree, but if you conserve your mana and use it for the right reasons it shouldn't be a problem.
The extra health and armor let you stay in lane much longer.
The 9 points in the Defense tree i ussually run with Durability and Veteran's Scar but if i have a low sustain support like Nunu, Leona or Blitzcrank i go with Vigor since it keeps you in lane for much longer and you can trade some auto-attacks without too much concern.